[Bug] Web UI spawns duplicate MCP server waves during active session

[kokucoding]

Environment

• OpenCode version: 1.1.16
• OS: Linux (Contabo VPS)
• Access: opencode web --port 4096 via Cloudflare tunnel

Bug Description

The Web UI spawns multiple complete waves of all configured MCP servers during a single session, causing duplicate tool responses (e.g., speak tool speaks twice).

Evidence

Process snapshot showing duplicates:

Web UI (PID 1103894) children:

WAVE 1 (08:49:33):
  1104065 memory-mcp
  1104066 tunnel-mcp
  1104067 speak-mcp      ← First instance
  1104073 port-manager-mcp
  ...

WAVE 2 (10:33:58 - 1hr 44min later):
  1110223 memory-mcp     ← Duplicate!
  1110224 tunnel-mcp     ← Duplicate!
  1110225 speak-mcp      ← Duplicate!
  1110226 port-manager-mcp
  ...

All 8 MCP types spawned twice, totaling 16 processes from one Web UI instance.

Steps to Reproduce

1. Start opencode web --port 4096
2. Access via browser, start a conversation
3. Wait ~30 minutes or make additional requests
4. Check: pstree -p $(pgrep -f "opencode web")
5. Observe: Multiple instances of each MCP type

Expected Behavior

Each MCP server should spawn exactly once per Web UI instance.

Actual Behavior

MCPs spawn in waves (observed 2+ waves), causing:

• Duplicate tool responses (speak speaks twice)
• Resource waste (double memory/CPU usage)
• Confusion about which instance handles requests

Workaround

Periodic cleanup script that kills duplicate MCPs (keeping lowest PID).

Related Issues

• #6633 - MCP not terminated after session (different: orphans on exit)
• #7261 - MCP orphans after crash (different: our duplicates spawn while running)